Underbody shield compositions and articles that provide enhanced peel strength

Abstract

A thermoplastic composite article comprising a porous core layer comprising a plurality of reinforcing fibers, a lofting agent and a thermoplastic material is provided. In certain instances, the article further comprises a skin layer disposed on the core layer and an adhesive layer between the core layer and the skin layer. In some configurations, the adhesive layer comprises a thermoplastic polymer and an effective amount of a thermosetting material to provide a post-molding peel strength between the skin layer and the post lofted core layer of at least 0.5 N/cm (in either or both of the machine direction or cross direction) as tested by DIN 53357 A dated Oct. 1, 1982.

What is claimed is: 
     
       1. An automotive underbody shield configured to couple to an undercarriage of a vehicle, the underbody shield comprising:
 a thermoplastic porous core layer comprising a web of open celled structures defined by random crossing over of reinforcing fibers held together by a thermoplastic polymer resin, the thermoplastic porous core layer further comprising a lofting agent distributed homogeneously through the thermoplastic porous core layer, wherein the lofting agent is effective to increase a thickness of the thermoplastic porous core layer upon exposure to heat to provide a post-lofted porous core layer, wherein the thermoplastic porous core layer comprises a porosity between about 20% to about 80% by volume, 30 weight percent to 70 weight percent reinforcing fibers, and 2 weight percent to 10 weight percent lofting agent; 
 a scrim disposed on a first surface of the post-lofted core layer, wherein the scrim comprises a basis weight of at least 65 gsm; and 
 an adhesive coating on the first surface of the post-lofted core layer and between the post-lofted core layer and the scrim, wherein the adhesive coating comprises a thermoplastic polyolefin polymer mixed with a thermosetting material, wherein an amount of the thermoplastic polyolefin polymer in the adhesive coating is greater than an amount of the thermosetting material in the adhesive coating, wherein a basis weight of the post-lofted core layer is less than 3000 gsm, wherein a post-molding peel strength between the scrim and the post-lofted core layer is at least 0.5 N/cm in the machine direction and at least 0.5 N/cm in the cross direction as tested by DIN 53357 A dated Oct. 1, 1982, and wherein the exterior automotive underbody shield comprises at least one drawn area with a depth of 5 cm or more without breakthrough. 
 
     
     
       2. The automotive underbody shield of  claim 1 , wherein the basis weight of the post-lofted core layer is about 1000 gsm, a basis weight of the adhesive coating is about 20 gsm, and a total thickness of the post-lofted core layer, adhesive coating and skin layer together is about 20 mm, wherein the thermoplastic polymer of the thermoplastic porous core layer is polypropylene and the reinforcing fibers of the thermoplastic porous core layer are glass fibers, and wherein the scrim is a polyethylene terephthalate scrim. 
     
     
       3. The automotive underbody shield of  claim 1 , in which the scrim is a non-woven scrim. 
     
     
       4. The automotive underbody shield of  claim 3 , in which the adhesive coating comprises polypropylene as the thermoplastic polyolefin material and an epoxy adhesive as the thermosetting material. 
     
     
       5. The automotive underbody shield of  claim 1 , in which the scrim is a non-woven scrim comprising an elongation at break of at least 20%. 
     
     
       6. The automotive underbody shield of  claim 1 , in which the scrim is disposed on an entire planar surface of the thermoplastic porous core layer. 
     
     
       7. The automotive underbody shield of  claim 1 , in which the scrim is disposed as a strip on a surface of the thermoplastic porous core layer. 
     
     
       8. The automotive underbody shield of  claim 1 , wherein the fibers dispersed within the thermoplastic polymer comprise fibers including a diameter greater than 5 microns and a length from 5 mm to 200 mm. 
     
     
       9. The automotive underbody shield of  claim 1 , wherein the thermoplastic polymer resin of the thermoplastic porous core layer is selected from the group consisting of a polyolefin resin, a thermoplastic polyolefin blend resin, a polyvinyl polymer resin, a butadiene polymer resin, an acrylic polymer resin, a polyamide resin, a polyester resin, a polycarbonate resin, a polyestercarbonate resin, a polystyrene resin, an acrylonitrile-styrene polymer resin, an acrylonitrile-butylacrylate-styrene polymer resin, a polyether imide resin, a polyphenylene ether resin, a polyphenylene oxide resin, a polyphenylenesulphide resin, a polyether resin, a polyetherketone resin, a polyacetal resin, a polyurethane resin, a polybenzimidazole resin, and copolymers and mixtures thereof. 
     
     
       10. The automotive underbody shield of  claim 1 , wherein the fibers of the thermoplastic porous core layer are selected from the group consisting of glass fibers, carbon fibers, graphite fibers, synthetic organic fibers, inorganic fibers, natural fibers, mineral fibers, metal fibers, metalized inorganic fibers, metalized synthetic fibers, ceramic fibers, and combinations thereof. 
     
     
       11. The automotive underbody shield of  claim 1 , in which the thermoplastic polyolefin polymer of the adhesive coating comprises polyethylene or polypropylene. 
     
     
       12. The automotive underbody shield of  claim 11 , in which the thermosetting material of the adhesive coating is present at less than 50% by weight of the adhesive coating. 
     
     
       13. The automotive underbody shield of  claim 12 , in which the thermoplastic porous core layer comprises polypropylene, glass fibers and microsphere lofting agents, the scrim is a polyethylene terephthalate scrim, and the adhesive coating comprises an epoxy adhesive as the thermosetting material, wherein the polyethylene or polypropylene is present in a greater amount than the epoxy adhesive in the adhesive coating, and wherein the post-molding peel strength between the polyethylene terephthalate scrim and the post-lofted core layer is at least 2.10 N/cm in the machine direction and at least 1.87 N/cm in the cross direction as tested by DIN 53357 A dated Oct. 1, 1982 at a tested molded thickness of 20 mm. 
     
     
       14. The automotive underbody shield of  claim 1 , further comprising an additional skin layer disposed on a second surface of the post-lofted core layer and an adhesive layer disposed on the second surface of the post-lofted core layer and between the additional skin layer and the post-lofted core layer, the adhesive layer comprising a thermoplastic polymer and a thermosetting material to provide a peel strength between the additional skin layer and the post-lofted core layer of at least 0.5 N/cm in the machine direction and at least 0.5 N/cm in the cross direction as tested by DIN 53357 A dated Oct. 1, 1982. 
     
     
       15. The automotive underbody shield of  claim 14 , in which the thermoplastic polymer of the adhesive layer comprises a polyolefin. 
     
     
       16. The automotive underbody shield of  claim 15 , in which the thermosetting material of the adhesive layer is present at less than 50% by weight of the adhesive layer. 
     
     
       17. The automotive underbody shield of  claim 16 , in which the thermosetting material of the adhesive layer is an epoxy adhesive. 
     
     
       18. The automotive underbody shield of  claim 1 , wherein 5% to 10% of the thermosetting material in the adhesive coating is cross-linked. 
     
     
       19. The automotive underbody shield of  claim 1 , further comprising additional thermosetting material disposed between the scrim and the thermoplastic porous core layer at the at least one drawn area with the depth of 5 cm or more. 
     
     
       20. The automotive underbody shield of  claim 1 , wherein the thermosetting material is present in the adhesive coating at less than 10% by weight of the adhesive coating.